Heating and cooling apparatus



- Dec. 8, 19421; .f A. v. sAMPsEL. 2,304,124

HEATING AN D COOLING APPARATUS Filed Feb, '4, 193s '2 sheets-sheet 1 @rf/Zub Kczng/Uel Dec. 8, 1942.

A. v. HEATING AND COOLING APPARATUS Filed Feb. 4, 1958 2 Sheets-Sheet 2 Alm Patented Dec. 8, 1942 Arthur V.

ration' of NewYork Sampsel, Mendota, IlL. asaigllor to Y Sears, Roebuck and Co., Chicago,

Application February 4, 1938, Serial No. 188,639

.acume (ci. zas-'41) ily invention reims to neat oontroi devices and has to do more particularly with the heating and cooling of one or a plurality of rooms or zones.

. It will be found applicable to systems employing air, water 'or other heat exchange medium.

It is an object of my invention to provide `mechanism for controlling the air conditioning of a plurality of zones automatically in suchl manner that each zone controls its own conditioning independently of the other zone or zones.

It is another object to provide mechanism for controlling the air temperature -of a plurality of zones automatically in such manner that each zone controls its own temperature independently of the other zone or zones.

It is a further object to provide a system operatlve in winter to heat and in summer to cool each of a plurality oi zones automatically independently of the other zone or zones. Another object is to provide a conditioning system in which the supply of. heat exchange medium and the operation of .valving means therefor are both governed` by the same thermo- A further object is -to provide Iconditioning',

system for a plurality of zones, wherein adamper or the like `associated with each zone and a supply of heat exchange medium are both controlled by the thermostat associated with said none, sc that said medium each zone independently of lionel.

the other zolle j or It is also an object to provide for automatically 'stopping fuel feed -to a furnace and at substantially the same time automatically commencing the cooling oi the furnace.

Also an object of the invention is the automatic cooling of the furnace when it is excessively heated.

A still further object resides in the provision of a master control with a winter. relay which normally 'completes a circuit to supply a'h'eat transfer medium when demanded by a thermostat and in the winter is automatically operative may be supplied to embodying features of my installed a damper-responsive control system invention.

Fig. 2 `is a detailed wiring diagram of the system appearing in Fig. 1.

Fig. 3 is a fragmentary diagrammatic view showing how a portion of the wiring of Fig. 2 may be modiiled to adapt the system to an installation which is not damper-controlled. as well as to one which is damper-controlled.

In the drawings, thenumeral I0 represents a iloor of a building, separating the basement l2 from the living or other quarters, which may be divided by walls such as the wall I3 into enclosures or zones lia and lsb.

In the basement I2 there Il and a furnace F, which'may be of the hot air type, as shown, and adapted for coal burning.

lAn underfed ,stoker 2i comprising a screw con surrounded by a casing or veyor 22 extends from the bin to the furnace. A suitable motive means S is 'provided for operating the conveyor for feeding coal from the bin to the furnace, and provided, operated by a motor B.

For illustrative purposes only, I have elected to show and describe a furnace of the hot air type,

eating through a plenum chamber 3| with air fines or ductsja and 33h, whereby warm air in the winterand cool air in the summer, when the furnace is not used, is conveyed to the respective zones or rooms whose temperatures are I B through connections and onamasterpanelasindbcated generan? ,at M.

by a lire control'to open. that circuit and close a fuel feed circuit regardless of whether or not the thermostat is demanding heat.

Further objects and advantages of mylinvention will appear as the description proceeds.

The invention will be understood upo'n reference to the following description andthe accompanying drawings, in which:

Fig. 1 is a fragmentary vertical sectional diagrammatic view through a' building in which is n This vtlium4 to the respective zones',

to be controlled. l

Each zone has a thermostat Ta, Tb, controlling a damper-control mechanism Da; Db, which in turri operates. in addition to adamper or valve for controlling ilow of heat exchange mea switch controlling blower or pump motor apparatus which may the stoker motor S and the be suitabflylmounted The panel apparatus appears in' detail diagrammatically in Fig. 2 and Y elsewhere.'

The winter operation of invention is substantially zone thermostat calls for heat, the appropriate damper will be opened and cause the stoker S and the blower B to be placed in operation. l It thereafter, and beforesaid thermostat has demanded a shutoff, a thermostat in another zone calls for heat, the appropriate damper for such other zone will be opened. However. since the stoker and blower are already in operation no alteration in the performance of these elementsV will occur. procedure, of course, will be the same for the apparatus or my is provided a cosi bm' a blower or fan 21, is also bonnet Il communil it lS any number of zones, the demand ior heat in any additional zone resulting merely in the opening oi the appropriate damper while the stolzer and blower continue to operate, so long as at least one thermostat calls for heat. As long as at least one thermostat demands heat, the electrical circuits controlling the stoker and blower will be closed and, therefore, the demand by any other thermostat that heat be shut oil' will result merely in the closing of the damper corresponding to such other thermostat without aecting the Stoker or blower. In other words, under normal conditions, the stoker and blower will not shut down until all of the thermostats have ordered a discontinuance of heat.

A time fire pilot control is provided to operate the stoker at suitable intervals in mild winter weather to keep the re from going out.

The above zone and time controls are subject to the following exception, however. In the event that the furnace becomes heated above a predetermined temperature, the electric circuit controlling the stoker will open and will remain open at least as long as said temperature is exceeded. While the stoker vis thus shut down, the furnace temperature may increase, due to residual heat or heat from a banked ilre, for example. with ordinances, munitures when the medium is hot air. In the eventA any zone calls for heat while the furnace temperature is above the predetermined stoker cutoi temperature and below said prescribed blower cutoi temperature, the blower will operateto supply the demand, notwithstanding that the stoker is not in operation. When again at or below the stoker cutoii' temperature, the stoker and blower are controlled as set forth above.

To convert the apparatus to summer operation "40 the furnace is erect of which is to shut on the Stoker 'and enable dampers to operate the blower to supply cool basement or other air to the individual zones as required by the respective zone thermostats. By throwing the same switches again, the apparatus is prepared for winter operation.

By a simple expedient. apparatus on the master panel may be adapted for operation with or without damper control, as desired.

Throughout this specication, unless otherwise specified or as may be gathered otherwise from the context, "winter is to be considered as including the late fall and early spring, and summer as includingthe late spring and early fall, it being understood that these periods are variable in duration according to locality and the particular weather conditions prevailing.

The stoker S is operated when heat is called for by any zone or room thermostat, and independently of the zones by a clock, as long as the furnace is not excessively hot.

The stoker circuit as it is iniluenced by the zones will be described first. The Stoker-S is in series with a hand or other suitable switch 5l which is closed in the winter and open in the summer, so that the stoker operates only in the- 'Ihe switch 50 is in series with a safety or limit control thermostat switch 5i which is "l5 adapted to open and thereby stop the stoker when the furnace reaches a predetermined high temperature. A wire 5I connects the switch li to one side oi the line 54 available for the particular installation. From the other side of the line a wire 5l is connected to the blade 58 oi a single pole single throw relay 59, said blade being urged away from the relay contact 6I by a springE 62. The contact 6| is connected by a wire IQ to the stoker S, thereby completing the zone-controlled stoker circuit. With winter conditions prevailing, so that and with the safety switch 5| closed, i. e.;"when the furnaceis not above a predetermined ternperaturepthe operation oi' the Stoker in this circuit is dependentonvthe closing of the switch of the relay 59,

'I'he coil 66 of the relay Slis connected by a wire i1 to the low voltage side 68"(1! a transformer 1I connected to the line 54. A wire 1| connects the other end of the transformer side n to a post 12, and a wire 'Il extends from the post to the blade 15 of a switch 1l associated with each zone. Each switch 1l has a contact 1l. The blade is urged by a spring 1l away from the associated contact 1l.V Each switch li is controlled by a room thermostat, as will be explained in detail. A wire l0 connects each contact H to a second post Il, and a wire 82 completes the relay circuit to the relay coil 66.

- when any zone or room demands heat in the winter, the relay coil B6 is energized, causing the blades Il to engage the contact 6I and thereby close the stoker circuit for operating the stoker. and, as will appear, the blower. Y

There is likely to be a period from time to time during which ber of times per hour, for example, for any deaired duration each time;from, say, fifteen the switch 50 is closed,

seconds, more or less. to, say, seven minutes, more or less.

The stoker will be operated when either or both of the relay coils 59 and 98 are energized, i. e., when either one or more zones and/or the clock calls for heat, provided of course the stoker safety switch 5|l is closed.

The blower B is operative in the winter to deliver warm air and in the summer to deliver cool air. It may be connected by a wire I| to the blade III of a limit control switch ||2 which is preferably of the thermostat type and is adjusted to open when the temperature of the air in the furnace bonnet is too cool for introduction to a room or zone to which warm air is to be delivered by the blower: The contact ||3, engageable by the blade when the bonnet air is warm, is connected by a wire II5 to a side of the line 54. A second wire |I`| is extended from the blower B and is connected to a contact I I8 on the relay |00. The relay blade I04-is urged by the spring |05 into engagement -with the contact I I8, completing a blower circuit through the wire |03, relay switch contact 6I and associated blade 58, and

wire 58 to the other side of the line 54.

It has been seen that the zone-controlled relay l0 may operate to run the stoker S. It is now apparent that said'relay at the same time may cause operation of the blower B, provided that the air in the furnace bonnet is sufficiently warm to close the air limit switch I I2 and further that the clock does not cause the relay |00 to withdraw the blade |04 from the contact |I8. Tests have shown that periodic stopping of the blower by the clock has a negligible effect on the temperature of the zones. It will be appreciated that even while the blower is idle the warm air will pass such dempers as may be open and into the heat-demanding zones by natural draft.

It has been pointed out that the switch 5| will be open and stop the stoker at a predetermined furnace or bonnet temperature. The heat from the fuel in the furnace may raise the temperature` of the furnace substantially above that at which the switch 5I opens. The furnace nevertheless may have a safe operating temperature range above said predetermined temperature. To prev ent overheating, I provide a blower limit or emergency switch |22 which is normally open but is designed to close at the upper limit of said range and to maintain the blower in operation regardless o'f lack of zone demand and of the clock, until the furnace is cooled to a temperature preferably intermediate the limits of said range,

whereupon the switch |22 may open. Zone operation of the blower is not affected by the switch |22, but only by the clock. The switch |22 is connected by a wire |23 to the line 54 and by a wire |24 to the wire III, thereby by-passing the relay switches containing the blades 58 and |04, respectively, and closing a circuit controlling the blower. In a short time, say about one minute, more or less, the blower will discharge sufllcient air to effect the desired amount of cooling and thereby open the switch |22. In the event the dampers are closed during such emergency operation. of the blower, the air thus blown will pass by way of the usual clearance between the dempers and the duct walls. Or, such air may discharge through a back pressure by-pass (not shown) to the outside of the bonnet.

In a hot air installation a temperature range or differential of about 100 F. has been found satisfactory, although it is to be understood that the switches 5| and |22 may be adjusted or formed 75 -fed by the line 54.

to operate at any temperatures desired or required. For example, the switch 5I may open at a bonnet temperature of 300 F. and the auxiliary switch |22 may close at 400 F. and open at 375 F. When hot water is used, it is desirable to operate the switches 5| and |22 at the same time, a pump being of course vused in lieu of a blower. When steam is used, emergency means such as a blowoi valve may be employed so that the switch |22 may be dispensed with.

The operation of the stoker below the stoker cutoff temperature and of the blower below the blowe'r cutoff temperature is dependent on the controls already described.

In the summer it is desirable to operate the blower to furnish cool, basement or other air from the bonnet to the various zones, the furnace being of course unheated. Since the low limit air control switch I I2 for the blower will be open at such time, I provide a manual or other suitable switch |30 which is maintained open in the winter, so as not to overcome the effect of the opening of the switch I2, but is closed in the summer. At such time the blower limit switch |22 is of course open and the clock idle. The clock switch 92 should be open so that the blade |04 will be engaged with the contact ||8. If, when the clock switch 86 is opened for summer operation of the apparatus, the switch 32 happens to be closed, the cam mechanism may be adjusted to open said switch, as will appear. The blower circuit is therefore open and closed only when any one or more of the zone thermostat-controlled switches 18 closes, as has been pointed out.

The switch ||2 may be closed all of the time, if desired, or may be omitted and the wire ||0 directly connected with the wire I I5, when hot air is the heat exchange medium. When hot water or steam is the medium, the switch I I2 is not needed, so that said wires may be directly connected. In any such event it is apparent that the switch |30 would'not be needed.

I provide a simple yet unique control for the damper and switch IE associated with each zone.

l This control includes a damper motor |35 operatively connected, through lany suitable means, such as reduction gearing (not shown), with a crank arm |35 (Fig. '1) from which a connecting rod |31 extends to a crank arm |39 on a damper valve |40, the arrangement being such that in one stroke of the arm |36 the valve will open fully and in the return stroke the valve will close fully. The damper motor |35 turns a cam |43 adapted to close the switch 16 by moving the blade 15 against the action of the spring `|8 and into engagement with the contact and also adapted to start and stop the motor, as will appear.

The damper motor |35 is connected to the line 54 and is controlled by a switch |4'I having a blade |48 urged away from the contact |49 by a spring |50. This blade is adapted to be moved into engagement with the contact |49 when a relay coil |53 is energized. This coil is connected to the low voltage side |54 of a transformer |55, The coil |53 is connected to the blade I 51 of a single pole double throw switch |58, a spring |59 urging the blade into engagement with a contact |6| and the cam |43 being operative when moving the blade 15 of the switch- I6 to also move the blade |57, against the action of the spring |59, into engagement with the contact |52. These contacts lead respectively to winter poles |65 and |66 at one side, and to summer poles |68 and |69 at the other side, of a double pole double throw switch |10, said switch comprising an arm |1| having blades |13 and |14.engageable with the first pair of poles |35 and |55 in the winter and with the second pair of poles |53 and |33 in the summer. 'I'he switch blades |13 and |14 are connected respectively with the contacts and |11 of a single pole double throw thermostat |13, the movable blade |13 of which is connected to lthe low voltage side |54 of the transformer |55, completing various circuits including the relay coil |53. The blade |15 is adapted to engage the contact iliwhen heat is not demanded in the winter and when cooling is demanded in the summer, and to ensage the contact |11 when heat is demanded in the winter and when cooling is not demanded in the summer.

The operation of the damper control will now be described, first for winter conditions and then for summer conditions.

In the winter, the blades |13 and |14 are engaged with the poles |55 and |55, respectively. Let it be assumed that the zone under consideration is not demanding heat. At such time the thermostat blade |13 is engaged with the contact |15, and the damper is closed, the cam |43 being in its inoperative position so that the switch 15 is held open by the spring 13 and the blade |51 is engaged with the contact |3|. The cam should not be turning under such conditions because if it were it would cause the switch 15 to close and cause the stoker and blower to operate when heat is not wanted inthe zone. It will presently appear that with the circuit'arrangement referred to the cam under such conditions remains in an inoperative position.

Under the conditions Just stated, in order for the cam 43 to be idle, the switch |41, controlling the damper motor |35, which runs the cam, must be open and hence the relay coil |53, controlling the switch |41, must not be energized. This coil is in a circuit which includes the blade |51 and contact lil, contact |55, blade |14 and thermostat contact |11, but since the contact |11 is not engaged with the blade |15, the coil circuit is open, so that the switch |41 is open and hence the damper motor |35 and cam |43 are idle.

Now let it be assumed that the zone requires heat. The thermostat blade will snap into engagement with the contact |11, so that, following through the relay coil circuit from that point in the next previous paragraph, the circuit continues from the contact 11 through the blade |13 and low voltage side |54 of the transformer |55 back to the coil |53 and hence the circuit is closed. The coil accordingly closes the switch |41, starting the damper motor |35 and cam |43. The damper motor opens the damper while the cam vcloses the switch 13 and disengages the blade |51 from the contact 5|. As will be seen,

vthis disengagement opens the relay coil circuit and hence the damper motor switch |41 opens, stopping the damper motor. The parts are so arranged that this disengagement occurs just at or after the closing of the switch 15, so that the opening of the damper will be completed and the cam will stop at a position where it maintains the switch 13 closed against the action of the spring 13 and maintains the blade |51 in engagement with the contact |32 against the action of the spring |55.

|52, contact |55, blade |13 to thermostat contact |15 which is free of the thermostat blade I|2 will be closed if the air in the bonnet is sufflciently warm, as it is likely to be. In any event, the furnace will heat the air quickLy, so that this switch will close in a minute ortwoand thus operate the blower.

As has been pointed out, under normal conditions, when the pilot tire control, i. e., the clock, operates the stoker S, the blower does not operate, and this condition is naturally desirable when no heat is needed. -1f the zone at such time should be demanding heat its damper will be open so that there will be some delivery of warm air by natural draft. In cold weather the clock adjustment is preferably such as to operate the stoker sparingly inasmuch as the zones will make adequate demands on the Stoker to keep the fire from dying. Consequently the stoppages of the blower by the clock will beof such short duration as to not appreciably affect the comfort in the zones. When the weather is relatively mild the clock adjustment preferably will be such as to operate the Stoker more often or for longer periods because of the corresponding paucity of the -zone demand for stoker operation, and at such times it is accordingly desirable that the blower be idle, the dampers being closed.

The delivery of warm air will be continued until the switch 13 opens, and, as will be explained, this will occur when the thermostat |13 stops calling for heat, for then the thermostat blade |19 will separate from the contact |11 and become engaged with the contact |16.

It will be recalled that the damper motor |35 A and cam |43 stopped with ,the switch |41 open.

With the thermostat blade |15 engaged with the contact |11 and the blade |51 engaged with the contact |52, the relay coil circuit extends from the coil |53 through the blade |51, contact the damper open and the cam holding the switch 13 closed and the blade |51 free of the contact |5| and in engagement with the contact |32, and because the thermostat blade |15 was separated from the contact |16, the circuit oi the relay coil |53 was open. Now, however, that the thermostat blade |13 has become engaged with the contact |15, the circuit of the relay coil |53 is closed since it runs from said coil through the blade |51, contact |52, contact |33, blade |13. thermostat contact |13, thermostat blade |15, low voltage side |54 of the transformer |55 and back to the coil |53. Accordingly, when the thermostat blade |19 engages the contact |15 the coil |53 is energized, -closing the damper motor switch |41 against the action of the spring |53, starting the damper motor |35 and cam |43. '.Ihe cam turns, allowing the spring 15 to open the switch 13 and thereafter the spring |55 to withdraw the blade |51 from the contact |52, thereby opening the coil circuit so as to deenergize the coil |53 and allow the spring |55 to open the damper motor switch |41. When the damper motor stops, the damper is closed and thecam is in inoperative position, and since the switch 13 is now open. the stoker control relay coil 53 is deenergized and the relay switch 53 is open, so that the stoker and blower are both stopped. 4Now the conditions are the same as at the beginning of the cycl'e of operation just explained.

Thus it is clear that in the winter heat will be supplied to any zone demanding it, regardless whether any other zone is demanding it, and that heat will not be supplied to any zone not demandheat, to preclude overheating ci the furnace and will cool the furnace to a safe temperature before being turned off; that the blower will supply heat substantially whenever demanded', and the clock cannot operate the stoker nor prevent operation,

of the'blower while the furnace is within a predetermined temperature range. When hot water is the medium, emergency cooling of the furnace starts immediately upon stopping of the Stoker at a predetermined high temperature. When steam is the medium, emergency operation of a blow-oil valve will take care of the situation.

In the summer, the switch 15, controlling the stoker S, is thrown and maintained open, so that the `stoker and hence the furnace are not in operation. The stoker limit switch is closed but of course ineffectual, and the blower limit switch |22 is open. The clock switch 55 is open so that the clock is stopped. The switch |35, however,

as Just noted, the zones are comfortably cool so that none is demanding 4to be cooled. As the operation of all zones is the same. it will sumce if reference is made to but one zone.

It has been pointed out that in the summer the thermostatA blade is engaged with the contact |15 when coolingis demanded and with the contact |11 when cooling is not demanded. With the blade |15 engaged with the contact |11, the circuit of the relay coil |53 extends from one side of said coil through the blade |51,

Acontact |5|, pole |55, pole |55 and blade |13 to contact |15, which is free, so that the circuit is open and hence the coil is not energized, the switch |41 is open, the damper motor |35 and cam |43 are idle. the damper remains closed, the blade |51 continues engaged with the contact |5| and the switch 15 remains open so that the is closed, and since it is in parallel with the air limit switch ||2, it is immaterial whether the latter is open or closed. Now it will be observed that there is a blower circuit extending from the blower through the switch to one side of the line 54, from the other side of the line to the relay switch blade 55, associated contact 5|, wire |03, blade |04, held engaged with contact ||3 by spring |05, and wire ||1 back to the blower. Thus the closing of this circuit is dependent upon the positions of the blades 55 and |||4. 'Ihe blade |04 is moved from the contact ||5 when the coil v93 yis energized. To preclude such energization the clock-operated cam mechanism 55 is adjusted when the clock is stopped, so as to open the switch. 92 controlling said coil. 'Accordingly in the summer the blower circuit is dependent on only the switch blade 53, which is controlled by the relay coil 56 which is controlled by any zone switch 16. This switch is closed when the zone associated therewith .needs cooling and is'open when cooling is not demanded, as will appear.

Upon the arrival of summer the stokcr and blower will not be called upon at all for the supply of -heat- When there is no demand for heat, it `has been seen that the thermostat blade |13 is engaged with the contact |15, the damper mo-y tor |35 is stopped with the damper closed, and the switch |41 accordingly open and the cam |43 in inoperative position so that the switch 15 is open and the blade |51 engaged with the contact IBI, winter-summer switch handle being of course in its winter position with its blades |13 and |14 respectively engaged with the contacts |55 and |55.

With this arrangement prevailing, no closing of the switch 15 can occur rrr-liess heat is demanded. It is desirable to furnish sones with cool air during the summer, and that ma le possible by the system I have provided, f op tlnowing the switch handle ill to i' s position, when the blades |13 and il@ respectively engage the poles |55 and |58. For the purpose of explaining a cycle of summer operation, ist it be nsw sumed that. when the switch handle i "li is thrown blower B is not in operation.

- when the zone demands cooling, the thermostat blade |15 leaves the contact |11 and engages the contact |15, so thatthe above-referred to relay circuit continues from the contact |15, through the blade |15, low voltage side |54 of the transformer and back through the coil |53. closing its circuit. The coil thus energized closes the damper motor ,switch |41 against the action of the spring |55, closing the damper motor circuit so that said motor and the cam |43 commence turning, the motor opening the damp,- erand the cam operating to close the switch 15 vand theny to separate thev blade m from the contact |5I, breaking the circuit of the relay 'coil |53, allowing the spring |55 to open the damper motor switch |41, stopping the motor with Vthe switch 15 closed and the blade |51 engaged withthe contact.l |62. Closing of the switch, 15 closes the circuit of the relay coil 55 which,` thus energized, draws the blade 53 into engagement with the contact 5|. closing the blower circuit. The blower B operates, supplying the cool air in the bonnet to the zone.

.When the zone has Icooled sumciently, the thermostat blade |13 leaves the contact |15 and engages the contact |11. vThen the circuit of the relay coil |53 is closed, the current flowing from the coil through the blade |51, contact |52, pole |55, pole |55, blade |14, thermostat contact |11, thermostat blade |15, low voltage side |54 of the transformer |55, back to the coil |53. Thereupon thecoil |53 is energized.

closingvthe damper motor switch 41 againsty the action of the spring |53, starting the damper motor |35 and cam |43, the motor turning the damper toward closed position andthe cam allowing the spring 13 to open the switch 15, stopping the blower B.' and allowing the spring |53 to move the blade |51 away from the contact |53, thereby deenergizing the coil |53 so as to permit the spring |53 to open the switch |41, stopping the motor |35 with the damper closed and the cam in inoperative position. f'This completes the cycle of summer operation] and it will bef'ob` served that the blower will operate and deliver cool air as long as any one or more zones deit, and only to the zone or zones demand- When winter comes, the switch handle moved'to its winter position, where its blades |13 and |14 respectively engage the poles |55 and |55, the stoker controlling switch 5U is closedythe clock controlling switch 56 is closed I' and the switch |33 is opened. The winter cycle has already been explained.

It will be appreciated that if the heating me dium be water or any other substance the member B could be a pump and there would be a water jacket, for example, instead of a bonnet, pipes instead oi ducts, and radiators or unit heaters in the respective zones, as will be appreciated by those skilled in the art.

In Fig. 3 I have shown at M a unit like the unit M but having an additional binding post |85 and a single pole double throw switch |81 whose blade |90 is operative through 'contacts ISI and |92 to connect the posts 8| and |85 alternatively to the relay coil 66. 'I'he unit M, above described in detail, employing only the posts 12 and Il, is used when the stoker and blowerare controlled by the damper motors associated with the various zones, so that only one thermostat per zone is necessary. The unit M', however, is adapted for an installation where the stoker and blower are independent of the 'damper motor, as well as for one in which the stoker and blower are damper motor controlled. In the former type of installation, each zone has 4two thermostats, one to control the damper in a separate thermostat-damper motor circuit (not shown) and the other to control the stoker and blower independently of said circuit and through said unit M', employing said additional post |85 and said switch Ill. In suchcase the contact Ill' of each zone thermostat is connected to th`e post Ill, the contact |11' to the post 8|, and the thermostat blade |18' to the post 12, and the switch blade |80, which preferably is of the manual type, is connected in the summer with the contact HI and hence with l the thermostat blade |79', and in the winter with the contact |92 and hence with the thermostat contact |11.

Now, when the temperature of a zone is too great the thermostat blade Ill engages the contact 1l', and when heat is demanded the blade engages the contact |11. In the winter, the contact Ill' is disconnected from and the contact |11 is connected to the relay coil li. so that the coil is energized only when the blade engages the contact |11', to operate the stoker and blower, subject to the conditions noted above relative to clock and limit control operation. In thek summer, the stoker is inoperative, so that the coil 68 is employed to operate the blower, the contact |18' being connectedto and the contact |11' being disconnected from the relay coil, so that the coil is energized only when cooling is demanded. As in the case of the damper motor controlled installation, it will be observed that the stoker and blower controlling thermostats in the various zones are all connected in parallel so that as long as there is a demand for heat in. the winter or cooling in the summer, whether from only one or from more than one zone, the apparatus will function to supply such demand, the damper thermostat in each such demanding zone operating to open the associated damper to conduct the blown air into such zone.

When the unit M is used with damper control, the switch blade |90 will be at all times engaged with the contact |92 and the switches 1I connected to the posts 12 and 8|, as shown in Fig. 2.

The clock-operated cam mechanism for opening and closing the stacker-controlling switch l2 is operated at intervals which preferably may be by way of example a cam mechanism which, in a given period such as one hour, may operate the stoker one, two or four times, for anywhere from about 15 seconds, more or less, .to about seven minutes, more or less, each time. Thus the clock may operate the stoker throughout a range of from one 15 second period per hour to four seven minute periods per hour. It is to be understood that although in the ensuing description, reference is made specifically to the mechanism making possible the variations just mentioned, the same principles may be employed to provide for clock operation of the Stoker any desired fractional or integral number of times including three or above four and for any desired duration above seven minutes each time, per hour or per any other desired period.

Although I have shown a specific type of heating plant, including a coal stoker, it will be apparent to those skilled in the art that my invention is applicable to other types employing different types of fuel, such as oil, gas, etc., and that, as stated above, the heat exchange medium may be other than hot air, for example steam or hot water. The medium could be for purposes other than heating or cooling, as for example humidiilcation and fumigation, with or without the use of a heating apparatus.

The apparatus may include wall plugs (not shown) for expeditious connection to electrical outlet sockets leading to the line B4, which may afford 110 volts, 220 volts or any other voltage.

The invention obviously is applicable to one or more zones, regardless whether the zones comprise individual rooms or merely dierent parts of the same room, as in alarge oilice, factory, assembly hall, theater, etc.

Various changes coming within the spirit'of my invention may suggest themselves to those skilled in the art, and hence I do not wish to be limited to the specific embodiments shown or uses mentioned, except to the extent indicated in the appendedclaims, which are to be interpreted as broadly as the state of the art will permit.

I claim:

1. A system for controlling the temperature of a space, comprising a furnace, a fuel feed therefor, means for delivering a heat exchange medium from said furnace to the space, means for operating said feed and said delivering means to supply demands for the medium to the space, means for operating said feed to prevent dying of the fire and for rendering said delivering means inoperative at such time, means for discontinuing operation of said feed when the temperature of said furnace is excessive, and means for operating said delivering means notwithstanding suchv discontinuance and independently of the third mentioned means. l

2. A system for controlling the temperature of a plurality of zones, comprising a furnace, a fuel `feed therefor, means for delivering a heat exchange medium from said furnace to the individual zones, means for operating said feed and said delivering means to supply demands for the medium to each zone independently of the other or others, means for operating said feed and for rendering said delivering means inoperative to prevent dying of the fire, means for discontinuing varied as to number and duration. For example, i in mild winter weather it naturally will not be necessary to run the stoker as often or for as long periods as in colder weather. In the illusn trated embodiment of my invention, I have shown operation of said feed when the temperature of said furnace is excessive, and'means for operating said delivering means notwithstanding such discontinuance.

ARTHUR V. SAMPSEL. 

